Help! SatNav/Stereo gremlins!

[shell320]

Thought it was worth a try to see if anyone on here has had this problem before or knows what the problem is.

Basically everything has turned itself on maximum volume and I cant turn it down. I have tried the steering control, the stereo control and the sat nav control but nothing works. Everything else works fine except the deafening volume. I have switched the amp off which makes it a little quieter but still not bearable. When the stereo and monitor are turned off the speakers still make a pulsing noise. It worked fine all day yesterday until the evening and I have never had this before.
If anone has any ideas or know of someone/somewhere that may be able to help I would be most grateful and my ears definately would.

Cheers Shell

[gf15]

remove the fuse for the radio & sat nav, leave them out overnight and replace. This cleared my issue where the radio would not switch off (and refused to change stations etc).